Acoustic warning device



March 16,1937. F. KO CH 25 19 ACOUSTIC WARNING DEVICE F'iled Aug; 15,19:53

v I I I UNITED STATES PATENT OFFICE 7 2,074,266 ACOUSTIC WARNING DEVICEFritz Koch, St. Ouen-sur-Seine, France, assignor to Robert Bosch Aktiit,Stuttgart, Germany Application August 15, 1933, Serial No. 685,271 InGermany September 30, 1932 3 Claims. (01. 177-7) 5 by an amplifyingacoustic conduit such as a horn, electromagnet, is screwed the base ofthe acoustic .5

trumpet or the like situated in front of this diaconduit 9,distance-pieces I being interposed. In- Phragm. this manner an annulargap sis formed, which is In such warning apparatus sometimes theosinterrupted only by the distance-pieces f, and cillations arising on,the one hand from the diawhich puts the chamber situated between thephragm and on the other hand from the column diaphragm and the neck ofthe acoustic conduit g 10 of air in movement in the acoustic conduitrecipinto communication with the exterior. rocally influence each other.This takes place This construction has the advantage that the moreespecially in an undesirable manner when same means are employed both tofasten the the acoustic conduit is of such proportions that acoustic airconduit to the casing of the device and its volume of air assumes a verymarked proper or to provide the opening communicating with the naturalperiod of vibration, for example, when its exterior. length and itsdiameter are in a definite propor- It will be understood that thisinvention is aption. Owing to the fact that this period of properplicable not only to warning apparatus having an oscillations maychange, for example, under the electromagnetic action, but also to thosewhich influence of atmospheric conditions, such a warnare operated inany other manner, where there is ing apparatus easily gets out oftune byan atmosco-ordinated action of a vibrating diaphragm and .pheric change;similarly, the adjustment of the an amplifying acoustic conduit.

tuning of the diaphragm in relation to the acous- I declare, that what Iclaim is: tic conduit and inversely is rendered more difiicult 1. Anacoustic horn comprising a casing, a diaby their reciprocal influence.phragm in said casing, means for vibrating said These defects areeliminated by the provision diaphragm, and an acoustic conduit fastenedto of an opening in the commencement of, or at the said casing by meansproducing an opening which base of, the acoustic air conduit, whichopening opens directly into the atmosphere between said communicateswith the exterior. casing and said conduit. According to the inventionthe said opening is 2. An acoustic horn comprising a casing, adiaproduced by the means for fastening the acoustic phragm in saidcasing, means for vibrating said air conduit to the casing of thewarning device. diaphragm, and an acoustic conduit fastened to Warningdevices constructed in accordance but spaced from said casing to providea ringwith the invention are shown by way of example like opening whichopens directly into the atmos in the accompanying drawing, in which:.-phere at the place where the conduit communi- 35 Figure 1 is alongitudinal axial section of'a cates with said casing.warningapparatus. 3. An acoustic horn comprising a casing, a dia- Figure2 is a transverse section of the apparatus phragm in said casing, meansfor vibrating said O the line AB of Figure 1. diaphr an acousticconduit, and means in- 40 In the construction shown in Figs. 1 and 2, aeluding, distance pieces for fastening said conduit 40 indicates thediaphragm, which is set in vibration to said casing and spacing ittherefrom whereby by means of the armature b of an electromagnet c anannular gap-which opens directly into the atand an interrupter, which isnot shown. The mosphere is formed between said casing and armature b andthe diaphragm ,a are connected by conduit which is interrupted by saiddistance a pin d. Furthermore, in this construction, a pieces. 45

The present invention relates to acoustic warning devices, moreparticularly intended for vehicles, in which the sound is produced by adiaphragm set in rapid vibration and then amplified plate e vibrating inunison with the armature and diaphragm is placed on an extension of thepin it.

This well-known method renders the sound of the warning device morepenetrating.

To the wall p of the warning apparatus which, in relation to thediaphragm, is remote from the FRI'IZ KOCH.

